The state Department of Energy and Environmental Protection will participate in Connecticut’s Historic Gardens Day at the Osborne Homestead Museum in Derby and at Harkness Memorial State Park in Waterford from noon to 4 p.m. Sunday, when admission will be free for all visitors.

Connecticut Historic Gardens Day, now in its 13th year, is designed to increase the awareness of the state’s unique historic sites and gardens and offers visitors an opportunity to explore a variety of historic garden styles, DEEP said in a news release.

The gardens at the Osborne Homestead Museum and at Harkness Memorial State Park are two of 15 historic gardens around the state.

Osborne Homestead Museum is at 500 Hawthorne Ave. off Route 34 in Derby. For information, call (203) 734-2513 or send an email to donna.kingston@ct.gov.

Harkness Memorial State Park is at 275 Great Neck Road.

Tours of the gardens, designed by one of America’s first female landscape architects, Beatrix Farrand, and the history of the Harkness Estate, Eolia, will be presented free of charge by park staff and Friends of Harkness volunteers.

Tours of the mansion will be available from 10 a.m. to 2 p.m. for a suggested donation.  For information, call (860) 443-5725.

Visit www.cthistoricgardens.org to learn about other events at the 15 historic gardens around the state.